Apparatus and method for measuring a nerve diameter

ABSTRACT

The present invention is generally directed to a nerve measurement apparatus, and to a method for measuring a nerve diameter. In one embodiment, the apparatus comprises an elongated shaft having a first end and an opposing second end, the first end and the second end being suitably configured to determine a diameter of a nerve. The first end may be further comprised of a pair of opposed prongs aligned with a longitudinal axis of the shaft and spaced apart by a predetermined distance to receive the nerve therebetween. The second end may be further comprised of a flexible self-coiling member having an inner diameter that conforms to the nerve diameter when the member is in a relaxed state.

CROSS-REFERENCE(S) TO RELATED APPLICATION

This application claims the benefit of Provisional Application No.60/519,508, filed Nov. 12, 2003.

TECHNICAL FIELD

The present invention relates generally to the measuring devices, and inparticular, to a device for measuring a nerve diameter.

BACKGROUND OF THE INVENTION

Methods for treating and controlling medical, psychiatric orneurological disorders through the application of a modulated electricalsignal to a selected nerve or nerve bundle in a patient are well known.Generally, the modulated signal is applied to the nerve or nerve bundleusing a neurostimulator electrode assembly that is surgically implantedin the patient. Briefly, and in general terms, the neurostimulatorelectrode assembly comprises one or more electrodes positioned within aresilient circumneural carrier that is configured to becircumferentially positioned on the nerve. In order for the electrode toestablish the requisite electrical contact with the nerve, the carriermust be able to securely hold the electrode against the nerve while notexcessively circumferentially compressing the nerve. One example of aneurostimulator electrode assembly is shown and described in U.S. Pat.No. 6,600,956 B2 to Maschino, et al.

In order to accommodate nerves or nerve bundles of various diameters,neurostimulator electrode assemblies are available in standardized sizesthat permit a surgeon to select the most appropriate size forimplantation in a patient. Currently, the selection of theneurostimulator electrode assembly is made based upon a visualinspection of the nerve diameter. Selection of the electrode assembly byvisual inspection has numerous drawbacks, however. If the surgeonselects an electrode assembly that has a diameter that is slightly toolarge, the electrodes within the assembly may fail to maintain adequateelectrical contact with the nerve, as previously mentioned. If anelectrode is selected that has a diameter that is too small, a nervecompression injury may result.

In order to overcome the shortcomings present in the visual estimationof a nerve diameter, the nerve diameter may be measured usingconventional calipers of suitable size and resolution. Despite thisobvious improvement, drawbacks nevertheless still exist. For example, asuitable measurement caliper may not be available to the surgeon whilethe implantation procedure is occurring. Even if a suitable caliper isavailable, conventional caliper devices generally possess relativelynarrow tips that may cause the relatively compliant nerve to flattenduring the measurement, thus rendering an inaccurate nerve diametermeasurement.

Therefore, there is a need in the art for an accurate and inexpensivedevice to accurately measure a nerve diameter in order to achieve aconsistent surgical outcome.

SUMMARY OF THE INVENTION

The present invention is generally directed to a nerve diametermeasurement apparatus, and to a method for measuring a nerve diameter.In one aspect, the apparatus comprises an elongated shaft having a firstend and an opposing second end, the first end and the second end beingsuitably configured to determine a diameter of a nerve. The first endmay be further comprised of a pair of opposed prongs aligned with alongitudinal axis of the shaft and spaced apart by a predetermineddistance to receive the nerve therebetween. The second end may befurther comprised of a flexible self-coiling member having an innerdiameter that conforms to the nerve diameter when the member is in arelaxed state.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view and a side view of a nerve measurement apparatusaccording to an embodiment of the invention.

FIG. 2 is an enlarged partial isometric view of one end of a nervemeasurement apparatus according to an embodiment of the invention.

FIG. 3 is another partial isometric view of one end of a nervemeasurement apparatus according to an embodiment of the invention.

FIG. 4 is a partial isometric view of an opposing end of a nervemeasurement apparatus according to an embodiment of the invention.

FIG. 5 is another partial isometric view of an opposing end of a nervemeasurement apparatus according to an embodiment of the invention.

FIG. 6 is still another partial isometric view of an opposing end of anerve measurement apparatus according to an embodiment of the invention.

FIG. 7 is still another partial isometric view of an opposing end of anerve measurement apparatus according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is generally directed to an apparatus and methodfor measuring a nerve diameter. Many of the specific details of certainembodiments of the invention are set forth in the following descriptionand in FIGS. 1 to 7 to provide a thorough understanding of suchembodiments. One skilled in the art will understand, however, that thepresent invention may be practiced without several of the detailsdescribed in the following description. Moreover, in the descriptionthat follows, it is understood that the figures related to the variousembodiments are not to be interpreted as conveying any specific orrelative physical dimension. Instead, it is understood that specific orrelative dimensions related to the embodiments, if stated, are not to beconsidered limiting unless the claims expressly state otherwise.

FIG. 1 is a front view and a side view of a nerve measurement apparatus10 according to an embodiment of the invention. The apparatus 10includes an elongated shaft 12 having a first end 14 and a secondopposing end 16. The shaft 12 may be formed to have any suitable lengthL, but in one particular embodiment, the shaft 12 has a length L ofapproximately about 10 centimeters. Although FIG. 1 depicts the shaft 12as a substantially straight, elongated member, it is understood that theshaft 12 may include bends or possess an overall curvature in order toallow the apparatus 10 to be more easily manipulated by the surgeon. Theshaft 12 may be fabricated from any semi-rigid polymeric materialsuitable for use in surgical procedures and compatible with conventionalsterilization procedures. In addition, the polymeric material comprisingthe shaft 12 may include a radio-opacifier, such as compounds of barium,or other materials, so that, in the event the apparatus 10 inadvertentlyremains in a patient's body following an implantation procedure, theshaft 12 may be conveniently imaged using an X-ray procedure. The shaft12 may also include various color pigments so that the shaft 12 iseasily visible. In another particular embodiment, one or more colors maybe selected to correspond to a selected nerve diameter, as will bedescribed in greater detail below.

Still referring to FIG. 1, the first end 14 includes a pair of spacedapart prongs that are substantially aligned with a longitudinal axis ofthe apparatus 10. The first end 14 will be described in greater detailbelow in connection with another figure. The second end 16 includes aflexible and self-coiling member 20 having a pull tab 18 fixedlyattached to the member 20. The second end 16 will also be described ingreater detail below in connection with another figure.

FIG. 2 is an enlarged partial isometric view of the a nerve measurementapparatus 10 according to an embodiment of the invention that shows, inparticular, the first end 14 of the apparatus 10. As described brieflyabove, the first end 14 includes a pair of spaced-apart prongs 19 thatare substantially aligned with the longitudinal axis of the apparatus10. In one particular embodiment, the first end 14 has a dimension “a”that is approximately about 2 millimeters, a dimension “b” that isapproximately about 8 millimeters, and a dimension “c” that isapproximately about 2 millimeters. Referring now to FIG. 3, the prongs19 are suitably spaced apart and suitably dimensioned to accommodate anerve between the prongs 19 and to permit a diameter of the nerve to beaccurately and rapidly determined.

Turning now to FIGS. 4 and 5, a partial isometric view of the second end16 of the nerve measurement apparatus 10 according to an embodiment ofthe invention is shown. The second end 16 includes a self-coiling member20 that is positioned in a fully-coiled configuration, as shown in FIG.4, when in a fully relaxed state, and also may be uncoiled by applying apulling force to the pull tab 18, as shown in FIG. 5. In a particularembodiment, the self-coiling member 20 may have a width “e” ofapproximately about 3 millimeters, and a diameter “f” of approximatelyabout 2 millimeters when the member 20 is in the relaxed state. When theself-coiling member 20 is in the uncoiled state, a nerve may bepositioned adjacent to an interior portion of the member 20. The pullingforce on the pull tab 18 may then be relaxed, allowing the member 20 toreturn to a coiled state and circumferentially surround the nerve.Accordingly, a diameter of a nerve may be made based upon the observedclosure of the member 20 about the nerve, as will be discussed ingreater detail below. The member 20 may be comprised of any resilientpolymeric material capable of sufficient flexure, such as varioussilicone materials. In one particular embodiment, the member 20 may beformed from SILASTIC, available from the Dow Corning Corp. of Midland,Mich.

Referring now to FIGS. 6 and 7, another partial isometric view of thesecond end 16 of the nerve measurement apparatus 10 according to anembodiment of the invention is shown. Many of the specific details ofthe second end 16 have been described in detail above, and in theinterests of brevity, will not be described further. Instead, a methodfor measuring a nerve diameter using the second end 16 will now bedescribed. Referring specifically to FIG. 6, when a nerve is retainedwithin the fully coiled member 20 and an end portion 21 of the member 20abuts the shaft 12, the diameter of the nerve corresponds to the knowninner diameter of the member 20. Thus, the nerve diameter is easily andquickly determined. Referring specifically now to FIG. 7, when a nerveis retained within the fully coiled member 20 and an end portion 21 ofthe member 20 is spaced apart from the shaft 12 by a distance “g”, it isdetermined by inspection that the diameter of the nerve is greater thanthe known inner diameter of the member 20. Accordingly, anotherapparatus 10 having a member 20 with a larger inner diameter “f” (seeFIG. 4) may be selected in order to determine the actual diameter of thenerve.

From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. For example, certain featuresshown in the context of one embodiment of the invention may beincorporated into other embodiments as well. Accordingly, the inventionis not limited by the foregoing description of embodiments except as bythe following claims.

1. A nerve measurement apparatus, comprising: a body including a firstend and a generally opposing second end, the first end comprising a pairof opposed prongs spaced apart by a predetermined distance to receive anerve therebetween.
 2. The nerve measurement apparatus of claim 1,wherein the second end comprises a flexible self-coiling member thatuncoils in response to application of a force thereto and coils to an atleast partially relaxed state when the force is removed so that an innerdiameter of the flexible self-coiling member generally conforms to anexterior of the nerve when the nerve is received by the flexibleself-coiling member.
 3. The nerve measurement apparatus of claim 2,wherein the flexible self-coiling member comprises a tab attachedthereto.
 4. The nerve measurement apparatus of claim 1, wherein the bodycomprises a polymeric material.
 5. The nerve measurement apparatus ofclaim 2, wherein the flexible self-coiling member comprises a resilientpolymeric material.
 6. The nerve measurement apparatus of claim 5,wherein the resilient polymeric material comprises silicone.
 7. A nervemeasurement apparatus, comprising: a body including a first end and agenerally opposing second end, the first end comprising a flexibleself-coiling member that uncoils in response to application of a forcethereto and coils to an at least partially relaxed state when the forceis removed so that an inner diameter of the flexible self-coiling membergenerally conforms to an exterior of a nerve when the nerve is receivedby the flexible self-coiling member.
 8. The nerve measurement apparatusof claim 7, wherein the second end comprises a pair of opposed prongsspaced apart by a predetermined distance to receive a nervetherebetween.
 9. The nerve measurement apparatus of claim 7, wherein theflexible self-coiling member comprises a tab attached thereto.
 10. Thenerve measurement apparatus of claim 7, wherein the body comprises apolymeric material.
 11. The nerve measurement apparatus of claim 7,wherein the flexible self-coiling member comprises a resilient polymericmaterial.
 12. The nerve measurement apparatus of claim 11, wherein theresilient polymeric material comprises silicone.
 13. A nerve measurementapparatus, comprising: an elongated shaft including a first end and agenerally opposing second end, the first end including a pair of opposedprongs substantially aligned with a longitudinal axis of the elongatedshaft and spaced apart by a predetermined distance to receive a nervetherebetween, the second end including a flexible self-coiling memberhaving a tab attached thereto, the flexible self-coiling member uncoilsin response to application of a force to the tab, and the flexibleself-coiling member coils to an at least partially relaxed state whenthe force is removed so that an inner diameter of the flexibleself-coiling member generally conforms to an exterior of the nerve whenthe nerve is received by the flexible self-coiling member.
 14. The nervemeasurement apparatus of claim 13, wherein the elongated shaft comprisesa polymeric material.
 15. The nerve measurement apparatus of claim 13,wherein the flexible self-coiling member comprises a resilient polymericmaterial.
 16. The nerve measurement apparatus of claim 15, wherein theresilient polymeric material comprises silicone.
 17. A method ofmeasuring a diameter of a nerve, comprising: providing a nervemeasurement apparatus comprising two opposed prongs spaced apart by afixed predetermined distance; and inserting the nerve between the twoopposing prongs.
 18. A method of measuring a diameter of a nerve using anerve measurement apparatus, the nerve measurement apparatus including aflexible self-coiling member, the flexible self-coiling member beingcoiled in a relaxed state and at least partially uncoiled in a tensionedstate, the method comprising: uncoiling the flexible self-coilingmember; at least partially enclosing a portion of the nerve with theuncoiled flexible self-coiling member; allowing the flexibleself-coiling member to return to at least a partially relaxed state sothat the flexible self-coiling member coils to at least partiallyenclose the portion of the nerve; and determining the diameter of thenerve from the extent that the flexible self-coiling member encloses thenerve.
 19. The method of claim 18, wherein the act of uncoiling theflexible self-coiling member comprises applying a force to the flexibleself-coiling member.
 20. The method of claim 18, wherein the act ofallowing the flexible self-coiling member to return to at least apartially relaxed state comprises removing a force applied to theflexible coiling member.
 21. The method of claim 18, wherein the act ofdetermining the diameter of the nerve comprises determining a distancethat an end portion of the flexible self-coiling member is offset from areference position when the flexible self-coiling member is in therelaxed state.